The study found that both men and women do not realise how early the brain function begins to deteriorate.

More than half (56%) of those surveyed thought the brain did not begin to decline until age 45 or later. But expert medical opinion claims deterioration can set-in as early as 18. Only 55% of respondents said they thought the brain needed any sort of training.

The results come despite most people reporting that their brain function was in decline. Just under one in three (30%) felt their brain had deteriorated in the last two years and 57% thought their brain had declined in the last five years.

The report showed:

32% of people do not take any exercise to stimulate the brain

62% of people choose watching television as a way to stimulate their brain

68% of people believe ad-hoc learning is more beneficial than structured learning

17% of people choose evening classes as a form of brain training.

The need for people to train their brain to halt decline is essential, according to Ian Robertson, professor of psychology at Trinity College Dublin.

“Our brains need to be stimulated and challenged through ongoing learning in the same way as our bodies need to be kept fit,” he said. “This will ensure we see off the ravages of time, which contribute to the decline of cognitive power.

“Continually refreshing your skills and knowledge is important at every stage and age in life,” he added, “and the benefits will last an entire lifetime.”

Learning a new skill, such as speaking a foreign language or taking an evening class in computer literacy are two of the most effective ways to stimulate the brain as they challenge the memory, attention and thinking centres of the brain in a comprehensive fashion, according to medical experts.